Method of assembling valve

ABSTRACT

A valve having seats made of axially separable, inner and outer parts which may be moved to positions, during assembly of the valve, permitting adjacent parts of the valve body to be welded and the weldments to be stress relieved without damage to seal rings carried by the seats.

United States Patent Allen 1451 Dec. 11, 1973 [54] METHOD OF ASSEMBLINGVALVE 3,155,368 11/1964 Shofer 29/157.1 R UX 3,235,226 2/1966 Allen251/315 X [75] Invent Herbert Allen 3,263,312 8/1966 Shofer 29/1571 R[73] Assignee: Cameron Iron Works, Inc., 3,545,721 12/1970 Shefer251/315 X Houston Tex. 3,657,783 4/1972 Ellis 29/157.1 R 3,666,2375/1972 Piccardo 251/367 [22] Filed: Jan. 24, 1973 3,678,556 7/1972Shofer 29/l57.l R

4 [21] Appl No 3265 2 Primary Examiner-J. Spencer Overholser RelatedU.S. Application Data Assistant ExaminerR0nald J. Shore [62] Division OfS61. NO. 184,727, Sept. 29, 1971, Pat. t rn y-Mar in B. Eickenroht [52]U.S. Cl. 29/l57.1 [57] ABSTRACT 51 1111.01 821d 53/00 A valve havingSeats made of axially separable, inner [58] Field 61 Search 29/1571;137/315, and outer Parts which may be moved to Positions,

137/24 22; 251/143 174 3 5 31 3 7 ing assembly of the valve, permitting.adjacent parts of the valve body to be welded and the weldments to be[56] References m stress relieved without damage to seal rings carriedby UNITED STATES PATENTS the Seats- 2,890,017 6/1959 Shofer 251/367 X 22Claims, 10 Drawing Figures SHEET 2 BF 4 PATENTED DEC 1 1 I975 METHOD OFASSEMBLING VALVE This is a division of application Ser. No. 184,727,filed Sept. 29, 1971 now U.S. Pat. No. 3,732,885.

This invention relates generally to valves. More particularly, itrelates to improvements in valves of the type shown in U.S. Pat. No.3,315,697, wherein separate parts of a central portion of the valve bodyare welded along their longitudinal edges to capture a closure membertherein for rotation between open and closed positions and form achamber about the closure having openings in each side. A seat ismounted within a tubular portion of the body which is joined by a girthweld to the central portion thereof in surrounding relation to each ofthe openings.

As shown in the aforementioned patent, a seal ring is carried on theinner end of the seat to engage the closure, and another seal ring isarranged between the outer diameter of the seat and the tubular bodyportion to seal between them. Since the seat extends through the sideopening in the central body portion, the seal rings are in closeproximity to the welds. Inasmuch as the heat radiating from the weldingoperations could ruin these metal rings, it has been proposed tocirculate water around them during this time.

However, not even this procedure is adequate to protect the seal ringsfrom the higher and more sustained temperatures incurred instress-relieving the weldment. Furthermore, clue to the disposal of theseat across the inner side of the weldment, it has been difficult toX-ray the girth weld to detect imperfections.

An object of this invention is to provide a valve of this type which maybe assembled without the necessity of circulating coolant past the sealrings or other parts of the seats susceptible to damage during thewelding operation.

Another object is to provide a valve of this type in which theweldrnents may be stress-relieved without damageto these seat parts.

A further object is to provide a valve of this type in which the girthweld may more readily be X-rayed.

Still another objectis to provide a method of assembling a valve which"enables oneor more of the foregoing objectsto be accomplished with amini'mumof a time, expense and effort.

These and other objects are accomplished, in accordance with theillustrated embodiments of the invention, by a valve in which the sealrings or other parts of the seat susceptible to damage by the weldingand related operations may, despitetheir capture within the valve body,be arranged in positions within the valve bodyremote from the weld areaduring such operations and then, upon completion thereof, moved withinthe valve body to the positions they normally occupy near such area forengaging between the valve body and closure member. Thus, each seatcomprises separable inner and outer annular parts, withthe inner partnormally engaging between the closure member and outer seat part and theouter seat part normally engaging between the inner seat part and thetubular body portion. The closure member and central body portion are sospaced that the inner seat part, when separated from the outer seatpart, may be arranged between them in its remote position and then movedbetween them to its normal position. The outer seatpart is slidablelongitudinally within a recess in the tubular portion so that, whenseparated, itmay bearranged inits remote position by being slid awayfrom-the closure member and then slid back toward the closure member toits normal position.

The inner seat part may carry a seal ring on its inner end which engagesthe ball closure, and the outer part is axially slidably mounted withinand sealed with respect to a recess in the tubular body portion by aseal ring arranged between them. The inner and outer seat parts aresealed with respect to one another by a seal ring between them, and theseat is yieldably urged against the closure by spring means preferablydisposed in the recess outwardly of the seat. By virtue of thisinvention, these seal rings, as well as other portions of the seatotherwise subject to damage, are protected from the welding and relatedoperations.

In one illustrative embodiment of the invention, wherein each openingfrom the chamber is smaller than the inner seat part, the inner seatpart is arranged between the closure and the parts of the central bodyportion as the longitudinal edges of the latter are welded together.More particularly, in order to prevent damage to seal rings carried bythe inner seat part, such part is arranged in a position remote from theweld and between the closure and the central body portions as they arewelded together. The illustrated closure is a ball which preferably hasstems on its opposite ends rotatably joumaled in the centralbody portionas its separate parts are connected together, and each inner seat partis intermediate the stems when arranged in such remote position.

In a second illustrative embodiment of the invention, each side openingis larger than the inner seat part so that the inner seat part may bemoved therethrough subsequent to welding of the separate parts of thecentral body portion. However, in this embodiment as well as in thefirst embodiment, the inner seat part may be arranged, prior to thewelding of a tubular portion to the central body portion, in a positionin which it is to one side of and thus remote from an opening in thechamber. In the case of the first embodiment, this requires movement ofthe'inner seat part from its position during formation of the weldsbetween the longitudinal edges of the central body portion. In the caseof the second embodiment, the inner seat part may be moved directly intosuch position upon movement through a side opening. I

With the inner seat part so displaced, the outer seat part is insertedinto the outer end of a recess in the tubular body portion, and thus toa position remote from the area to be welded to the central bodyportion. The tubular portion is then welded to the central body portionand the weld is heat-treated and X-rayed. If a similar structure is tobe welded to the opposite side of the central body portion, there willhave been two inner seat parts displaced for the first girth weld andthen repositioned for the second.

The outer seat part is then moved inwardly to permit insertion of theseal ring for sealing between the seat and the recess, whereupon theinner and outer seat parts are moved to assembled position and thespring means inserted into operative position within the recess foryieldably urging the seat parts together, and thus the inner seat partagainst the ball closure.

Preferably, the inner seat part includes a seal ring for sealing betweenthe inner and outer seat parts so that when the inner seat part of thefirst embodiment is in its position remote from the welding of thelongitudinal edges of the central body portion, it is removed from theheat thereof. Also, when the inner seat part of either embodiment ispositioned to one side of the chamber opening, they are removed from theheat of the girth welding and stress-relieving operations.

In the drawings, wherein like reference characters are used throughoutto designate like parts:

FIG. 1 is a side view, partly in section, of a ball valve assembled inaccordance with the first-mentioned embodiment of the invention; 4

FIG. 2 is a sectional view of the valve, as seen along broken line 2-2of FIG. 1, during welding of a longitudinal edge along one side of thecentral body portions, and with the inner'seat parts in positions remotetherefrom;

FIG. 3 is a sectional view of the valve as seen along broken line 3-3'of FIG. 2, showing the longitudinal edges welded and the inner seatparts moved to positions preparatory to formation of one of the girthwelds;

FIG. 4 is a sectional view of the valve as seen along broken line 4-4 ofFIG. 3, during formation of such girth weld;

FIG. 5 is an enlarged sectional view of a portion of the valve of FIGS.1 to 4, with the outer seat part moved inwardly from its position inFIG. 4 and the seal rings inserted into a groove within the recess inthe tubular body portion;

FIG. 6 is a view similar to FIG. 5, but with the assembly of the valvecompleted;

FIG. 7 is a perspective view of a part of the spring means;

FIG. 8 is an enlarged sectional view of a portion of a valve duringassembly in accordance with the secondmentioned embodiment of theinvention, wherein the inner seat part has been moved through thechamber opening and into a position remote from the area thereabout tobe welded;

FIG. 9 is a view similar to FIG. 8, but upon completion of the weld andmovement of the outer seat part inwardly to facilitate installation ofseal rings; and

FIG. 10 is a view similar to FIG. 9, but with the assembly of the valvecompleted.

With reference now to the details of the abovedescribed drawings, thevalve made in accordance with the first embodiment of the invention, andindicated in its entirety in FIG. 1 by reference character 20, includesa valve body 21 having a flowway 22 there through, and a ball closure 23having a port 24 therethrough and rotatably mounted within the valvebody for selectively opening and closing the passage through theflowway. The ball closure is arranged concentrically within aspherically shaped chamber 25 intermediate the opposite cylindrical endsof the flowway and has upper and lower stems 26 and 27 journaled withinbearings 26A and 27A formed in the valve body at the upper and lowersides of the chamber. The upper stern extends through a seal ring in theupper bearing and has an exterior end to which a suitable operator (notshown) may be connected for rotating the ball closure.

An annular seat 28 is slidably mounted within a annular recess 29 ateach intersection of flowway 22 with chamber 25. The inner end of eachseat sealably engages the ball closure, and the outer diameter of aportion of each seat is sealably slidable within its recess 28. Theinner diameter of the seat forms a continuation of flowway 22. Therightand left-hand sides of the valve may be identical.

Chamber 25 is formed within a central body portion comprising upper andlower hemispherically shaped parts 31 and 32, respectively. The adjacentside edges of these parts are disposed generally longitudinally in aplane perpendicular to the axis of rotation of the ball closure, and arewelded together, as indicated at 30, to mount stems 26 and 27 inbearings 26A and 27A, respectively. The connection of the parts alsoforms flowway openings 33 in opposite sides of the chamber. The diameterof openings 33 is less than the outer diameter of seat 28.

The valve body 20 also includes a pair of tubular portions 34 eachhaving an inner end welded at 35 to an annular surface on the centralbody portion surrounding an opening 33 therein. Each seat 28 is axiallyslidably mounted within recess 29 extending axially outwardly from theinner end of one of the tubular portions, so that when the latter are soconnected to the central body portion, the seats 28 are arranged toextend through the openings 33 and thus across the inner sides of theweldments 35.

As best shown in FIGS. 5 and 6, each seat 28 includes inner and outer,axially separable annular parts 36 and 37, interfitted so as to maintainthem in axial alignment. The outer part is axially slidable withinrecess 29 and spring means 50, in the recess behind the outer part,urges both parts toward the ball closure. A seal ring 38 is carriedon'the inner end of inner seat part 36 for sealably engaging the ballclosure, a pair of seal rings 42 and 43 are carried on the outer end ofseat part 36 for sealably engaging the inner end of outer seat part 37,and a pair of seal rings 39 in a groove 40 in recess 29 seams betweenouter seat part 37 and the recess.

The space S between the closure and chamber permits the inner part ofeach seat to be arranged in a position to one side of opening 33, sothat, as shown in FIG. 5, the outer seat part 37 may be moved axiallywithin recess 29 to an innermost position in which it extends throughopening 33 to engage the ball closure, as shown in FIG. 5. Prior toinsertion of spring means 50, the outer seat part may be moved to anouter position (not shown) in which it is also within opening 33, butspaced from the ball closure a sufficient distance to permit the innerseat part 36 to be moved from its position of FIG. 5 into the positionof FIG. 6 and thus into axial alignment with the outer seat part. Moreparticularly, the outer seat part 37 may be moved axially outwardly tothe position shown in FIG.'4, in which position its inner end isdisposed axially outwardly from the opening 33 and thus the inner sideof the weldment 35. Then, of course, with the inner seat part 36 in itsposition of FIG. 6, the outer seat part 37 may be moved axially inwardlyinto interfitting relation with the inner seat part, and, when the seatparts are so interfitted, they are sealed with respect to one another bythe seal rings 42 and 43.

To assemble the valve, the inner seat parts 36 are placed between theball closure and the upper and lower parts 31 and 32 of the central bodyportion as the latter are moved into positions about the ball closurepreparatory to welding one pair of longitudinal edges as at 30. As shownin FIG. 2, parts 36 are arranged in positions within the space S remotefrom each weldment, and thus in positions in which heat from theweldment will not damage the seal rings carried by the inner seat parts.The edges are welded by a torch T and the weldment may also bestress-relieved. Parts 36 are then moved to the other side of theclosure and the other pair of longitudinal edges is welded.

Preparation is then made for welding a tubular body portion 34 to thecentral body portion about one of the openings 33 by a girth weld 35.The inner seat parts may be moved within the space S into the positionshown in FIGS. 3, 4 and 5, which, in effect, involves turning one ofthem approximately 180 from the position it occupied during formation ofa weld 30. An outer seat part 37 is inserted in the inner end of atubular body portion which is then juxtaposed with the annular surfaceof the central body portions to which it is to be welded, as shown inFIG. 4. The outer seat part is preferably in its axially outermostposition. .A girth weld 35 is then formed, as by means of a weldingtorch T, and subsequently stress-relieved in any conventional manner.With the outer seat part-in the position shown in FIG. 4, the X-ray gunis able to take a clear picture of the weld 30 without interference withextraneous material cross its inner side. The other tubular body portionmay be assembled in similar fashion.

Upon completion of welding-related operations, outer seat part 37 ismoved inwardly to the position of FIG. 5, to uncover groove 40 in recess29 and thus permit seal rings 39 to be inserted through the tubular bodyportion and into such grooves. Seal rings 39 are resilient and, may becollapsed for insertion through the tubular body portion. When soinserted, the seal rings are located for sealing between the tubularbody portion and the outer seat part 37 when the latter is movedoutwardly into the position of FIG. 6.

Lubricant from an external source is supplied to a groove 45 about theinner end of the seat radially inwardly of the seal ring 38. For thispurpose, each of the inner and outer seat parts is provided with aseries of ports 46 and 47, respectively, connecting the groove 45 in theinner seat part with the groove 40 in which the seal rings 39 arearranged. These seal rings are held apart by a coil spring 48disposed'between them so as to sealably engage the outer diameter ofouter seat part 37 on opposite sides of the groove-47, and seal rings 42and 43 are so mounted on the outer end of the inner seat part 36 as toseal between the inner seat part and outer seat part radially outwardlyand inwardly, respectively, of the intersecting ports 46 and 47. Thus,lubricant fed from a suitable source through a port 49 in the tubularvalve body portion is confined for flow into the groove 47 and thus intothe groove 45. of course, the coil spring 48 may be collapsed in muchthe same manner as the seal rings 39 to permit it to be inserted throughthe tubular body portion. With outer seat part 37 moved outwardly asufficient distance, the inner seat part 36 is swung into the positionof FIG. 6. Then the outer seat part is moved inwardly into interfittingrelation therewith, as shown in FIG. 6, in which position seal rings 39seal between the outer seat part and recess 29.

Spring means 50 is then inserted through the tubular body portion andinto the recess 29 axially outwardly of the outer seat part. Severalsuch springs are well known in the art. As illustrated, spring 50comprises a plurality of spring segments 51 each comprising an arcuatearm having a button 52 at its opposite ends for engaging the outer endof the outer seat part, and a screw 53 threadedly carried intermediatethe buttons. With all segments in place within the recess, the screwsare extended to cause heads 54 to abut the end 41 of the recess and thuspermit a desired force to be transmitted to theouter seat part.

The second embodiment of the invention is much like the first in that,as illustrated in part in FIGS. 8 to 10, it is also made up of a valvebody having a central portion comprised of upper and lower partsconnected together along adjacent longitudinal edges which lie generallywithin a plane pernepdicular to the axis of rotation of a ball closure56 and which form a chamber 57 in which the ball closure 56 isconcentrically arranged and define openings 58 in opposite sides of thechamber. Also, the inner end of a tubular body portion 59 is welded at60 to an annular surface of the tubular body portion surrounding each ofthe openings 58; and, after assembly of the valve (FIG. 10), a seat 61is axially slidably mounted within a recess 59b extending outwardly fromthe inner end of the tubular body portion and having anouter end 74, so.as to extend through the opening 58 and engage at its inner end the ballclosure 56.

As in the first embodiment, the seat 61 includes an inner part 62 whichis axially separable from and interfittable with an outer seat part 63.Inner seat part62 carries a seal ring 64 on its inner side for sealablyengaging the ball closure, and seal rings 65 and 66 on its outer end forsealably engaging the inner end of the outer seat part 63 when the seatparts are interfitted.

Seal rings 67 and 68 arearranged between the outer di- 74a on the innerend of the inner seat part.

Spring means 70 is arranged within the recess 59b axially outwardly ofthe outer seat part 63 for urging the outer seat part and thus the innerseat part toward the ball closure 56. Spring means 70 also includes wavyspring segments 72 whose inner side engages the outer side. of seal ring68, and whose outer undulations are engaged by a segmented spring 73similar to that shown at in FIG. 6. Seal rings 67 and 68 arearranged ona reduced diameter portion 71 about the outer end of the outer seatpart.

In this second embodiment of the invention, the openings 58 in the sidesof the central body portion are larger than the outer diameters of innerseat parts 62, to that its notnecessary to arrange the latter betweenthe separate parts of such body portions as they are welded together.However, as in the first embodiment of the invention, in preparation formaking girth weld 60, the inner part 62 of each seat is movable withinannular space S between the closure member 56 and the wall of chamber57. Thus, the inner seats may be moved through chamber opening 58 andarranged in the positions corresponding to those illustrated in FIG. 4.Thus seal rings 64, and 66 carried thereon are remote from the heat ofwelding and stress-relieving.

The remaining assembly operations will'be obvious I from the descriptiongiven of the first embodiment.

From the foregoing it will be seen that this invention is one welladapted to attain all of the ends and objects hereinabove set forth,together with other advantages which are obvious-and which are inherentto the apparatus and method.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations. This is contemplated by and is within the scope of theclaims.

As many possible embodiments may be made of the invention withoutdeparting from the scope thereof, it is to be understood that all matterherein set forth or shown in the accompanying drawings is to beinterpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed 1. in a method inwhich a valve body is welded in an area near that normally occupied by aseat part captured within the body, the steps of arranging the seat partin a position within the body which is remote from said area, weldingsaid body in said area while the seat part is so arranged, and thenmoving said seat part to the position it normally occupies.

2. In a method of the character defined in claim 1, wherein the seatpart includes a rigid body and a seal ring.

3. In a method of assembling a valve wherein portions of a valve bodyare welded to one another to capture a closure member and part of aseat, and the seat part normally occupies aposition near the area of thebody to be welded, the steps of arranging the seat part in a positionwithin the valve body which is remote from said area, welding said bodyportions to one another while the seat part is so arranged, and thenmoving said seat part to the position it normally occupies.

4. ln a method of the character defined in claim 3, wherein the seatpart comprises a rigid body and a seal ring.

5. In a method of the character defined in claim 2, wherein the entireseat is captured within the body portions, and said seat part isseparated from the remainder of the seat for arrangement in saidposition.

6. In a method of assembling a valve wherein a closure member iscaptured within a central body portion and a tubular body portion iswelded to the central portion to surround an opening from the centralbody, and a seat mounted in the tubular bodyportion extends through theopening to engage the closure member, the steps of separating one partof the seat from the remainder thereof and arranging it in a positionwithin the valve body which is remote from the area to be welded,welding said tubular portion to said central portion while said seatpart is so arranged, and moving said seat part to a position in which itmay be engaged with the other seat part for extension through saidopening.

7. In a method of the character defined in claim 6, including the stepof stress-relieving the weld while said seat part is in its remoteposition.

8. In a method of the character defined in claim 6, including the stepof X-raying the weldment while said seat part is in its remote position.

9. In a method of the character defined in claim 6, wherein the seatpart is on the inner end of the seat for engaging the closure member andis arranged and moved between said closure member and central bodyportion.

10. In a method of the character defined in claim 6, wherein the seatpart is on the outer end of the seat for sliding within the tubular bodyportion toward and away from the closure member.

11. A method of assembling a ball valve, comprising the steps ofconnecting separate parts of a central body portion about a ball closureto form a chamber having an opening in the side thereof and to mount theclosure within the chamber for rotation between opened and closedpositions, arranging a first annular seat part in a position between theball closure and central body portion to one side of said opening,mounting a second annular seat part for sliding axially within anannular recess in the inner end of a tubular body portion, welding theinner end of the tubular body portion to the central body portion aboutthe opening therein, while the first seat part is in its position to oneside of said opening, moving said first seat part between the ballclosure and central body portion into another position in which it isaligned with said opening and the second seat part, moving the seatparts into interfitting relation with one another, and inserting a meansthrough the outer end of the tubular portion for yieldably urging saidsecond part against the first seat part and said first seat part againstthe ball closure.

12. A method of the character defined in claim 11, including the step ofmoving the outer seat part outwardly within the recess prior to weldingthe tubular body portion to the central body portion.

13. A method of the character defined in claim 11, including the step ofconnecting the separate parts by welding each side edge along a planegenerally perpendicular to the axis of rotation of the ball closure withthe first seat part arranged in a position between the ball closure andthe central body portion remote from said side edge.

14. A method of the character defined in claim 11, including the step ofmoving said first seat part through said opening in order that it may bearranged in said position between the closure member and central bodyportion to one side of said opening.

15. A method of the character defined inclaim 11, including the step ofproviding said first seat part with a seal ring mounted thereon to forman annular seal between said seat parts when they are interfitted andsaid second seat part is yieldably urged against said first seat part.

16. A method of the character defined in claim 11, including the step ofinserting a seal ring through the outer end of the welded tubular bodyportion into a position within the recess for sealing between saidrecess and the second seat part.

17. A method of the character defined in claim 16, wherein said sealring is inserted into a groove in said recess when said second seat partis moved toward the ball closure to permit access to the groove.

18. A method of the character defined in claim 17, including the step ofmoving the second part inwardly toward said ball closure to permitaccess to the groove prior to movement of the first seat part into theposition in which it is aligned with said opening, and then moving thesecond seat part outwardly to permit the first seat part to be movedinto said aligned position, whereby saidseat parts may be moved intointerfitting relation.

19. A method of the character defined in claim 11, wherein the ballclosure has stems on its opposite ends which are rotatably journaled inthe central body portion upon connection of its separate parts, and thefirst seat part is intermediate said stems when arranged in its positionto one side of said opening.

20. A method of assembling a ball valve, comprising the steps ofconnecting searate parts of a central body portion about a ball closureto form a chamber having a pair of openings therein and to mount theclosure within the chamber for rotation between opened and closedpositions, arranging a pair of first annular seat parts between the ballclosure and central body portion, mounting each of a pair of secondannular seat parts for sliding axially within an annular recess in theinner end of a tubular body portion, welding the inner end of eachtubular body portion to the central body portion about an openingtherein, while each of said first seat parts is in a position to oneside thereof, moving each said first seat part between the ball closureand central body portion into another position in which it is alignedwith an opening and a second body part, moving each pair of first andsecond seat parts into interfitting relation with one another, andinserting a means through the outer end of each tubular portion foryieldably urging said second part against the first seat part with whichit is interfitted and said first seat part against the ball closure.

21. A method of the character defined in claim 20, including the step ofconnecting the separate parts by welding their side edges together alonga plane generally perpendicular to the axis of rotation of the ballclosure with each of the first seat parts arranged in a position betweenthe ball closure and the central body portion which is remote from eachside edge as it is welded.

22. A method of the character defined in claim 20, wherein the ballclosure has stems on its opposite ends which are rotatably journaled inthe central body portion upon connection of its separate parts, and eachfirst seat part is intermediate stems when arranged in its position toone side of said one opening.

1. In a method in which a valve body is welded in an area near thatnormally occupied by a seat part captured within the body, the steps ofarranging the seat part in a position within the body which is remotefrom said area, welding said body in said area while the seat part is soarranged, and then moving said seat part to the position it normallyoccupies.
 2. In a method of the character defined in claim 1, whereinthe seat part includes a rigid body and a seal ring.
 3. In a method ofassembling a valve wherein portions of a valve body are welded to oneanother to capture a closure member and part of a seat, and the seatpart normally occupies aposition near the area of the body to be welded,the steps of arranging the seat part in a position within the valve bodywhich is remote from said area, welding said body portions to oneanother while the seat part is so arranged, and then moving said seatpart to the position it normally occupies.
 4. In a method of thecharacter defined in claim 3, wherein the seat part comprises a rigidbody and a seal ring.
 5. In a method of the character defined in claim2, wherein the entire seat is captured within the body portions, andsaid seat part is separated from the remainder of the seat forarrangement in said position.
 6. In a method of assembling a valvewherein a closure member is captured within a central body portion and atubular body portion is welded to the central portion to surround anopening from the central body, and a seat mounted in the tubular bodyportion extends through the opening to engage the closure member, thesteps of separating one part of the seat from the remainder thereof andarranging it in a position within the valve body which is remote fromthe area to be welded, welding said tubular portion to said centralportion while said seat part is so arranged, and moving said seat partto a position in which it may be engaged with the other seat part forextension through said opening.
 7. In a method of the character definedin claim 6, including the step of stress-relieving the weld while saidseat part is in its remote position.
 8. In a method of the characterdefined in claim 6, including the step of X-raying the weldment whilesaid seat part is in its remote position.
 9. In a method of thecharacter defined in claim 6, wherein the seat part is on the inner endof the seat for engaging the closure member and is arranged and movedbetween said closure member and central body portion.
 10. In a method ofthe character defined in claim 6, wherein the seat part is on the outerend of the seat for sliding within the tubular body portion toward andaway from the closure member.
 11. A method of assembling a ball valve,comprising the steps of connecting separate parts of a central bodyportion about a ball closure to form a chamber having an opening in theside thereof and to mount the closure within the chamber for rotationbetween opened and closed positions, arranging a first annular seat partin a position between the ball closure and central body portion to oneside of said opening, mounting a second annular seat part for slidingaxially within an annular recess in the inner end of a tubular bodyportion, welding the inner end of the tubular body portion to thecentral body portion about the opening therein, while the first seatpart is in its position to one side of said opening, moving said firstseat part between the ball closure and central body portion into anotherposition in which it is aligned with said opening and the second seatpart, moving the seat parts into interfitting relation with one another,and inserting a means through the outer end of the tubular portion foryieldably urging said second part against the first seat part and saidfirst seat part against the ball closure.
 12. A method of the characterdefined in claim 11, including the step of moving the outer seat partoutwardly within the recess prior to welding the tubular body portion tothe central body portion.
 13. A method of the character defined in claim11, including the step of connecting the separate parts by welding eachside edge along a plane generally perpendicular to the axis of rotationof the ball closure with the first seat part arranged in a positionbetween the ball closure and the central body portion remote from saidside edge.
 14. A method of the character defined in claim 11, includingthe step of moving said first seat part through said opening in orderthat it may be arranged in said position between the closure member andcentral body portion to one side of said opening.
 15. A method of thecharacter defined in claim 11, including the step of providing saidfirst seat part with a seal ring mounted thereon to form an annular sealbetween said seat parts when they are interfitted and said second seatpart is yieldably urged against said first seat part.
 16. A method ofthe character defined in claim 11, including the step of inserting aseal ring through the outer end of the welded tubular body portion intoa position within the recess for sealing between said recess and thesecond seat part.
 17. A method of the character defined in claim 16,wherein said seal ring is inserted into a groove in said recess whensaid second seat part is moved toward the ball closure to permit accessto the groove.
 18. A method of the character defined in claim 17,including the step of moving the second part inwardly towaRd said ballclosure to permit access to the groove prior to movement of the firstseat part into the position in which it is aligned with said opening,and then moving the second seat part outwardly to permit the first seatpart to be moved into said aligned position, whereby said seat parts maybe moved into interfitting relation.
 19. A method of the characterdefined in claim 11, wherein the ball closure has stems on its oppositeends which are rotatably journaled in the central body portion uponconnection of its separate parts, and the first seat part isintermediate said stems when arranged in its position to one side ofsaid opening.
 20. A method of assembling a ball valve, comprising thesteps of connecting searate parts of a central body portion about a ballclosure to form a chamber having a pair of openings therein and to mountthe closure within the chamber for rotation between opened and closedpositions, arranging a pair of first annular seat parts between the ballclosure and central body portion, mounting each of a pair of secondannular seat parts for sliding axially within an annular recess in theinner end of a tubular body portion, welding the inner end of eachtubular body portion to the central body portion about an openingtherein, while each of said first seat parts is in a position to oneside thereof, moving each said first seat part between the ball closureand central body portion into another position in which it is alignedwith an opening and a second body part, moving each pair of first andsecond seat parts into interfitting relation with one another, andinserting a means through the outer end of each tubular portion foryieldably urging said second part against the first seat part with whichit is interfitted and said first seat part against the ball closure. 21.A method of the character defined in claim 20, including the step ofconnecting the separate parts by welding their side edges together alonga plane generally perpendicular to the axis of rotation of the ballclosure with each of the first seat parts arranged in a position betweenthe ball closure and the central body portion which is remote from eachside edge as it is welded.
 22. A method of the character defined inclaim 20, wherein the ball closure has stems on its opposite ends whichare rotatably journaled in the central body portion upon connection ofits separate parts, and each first seat part is intermediate stems whenarranged in its position to one side of said one opening.